Fungi are plants which obtain their nutrition from a preformed organic carbon source. The body of the fungus (hyphae) secretes enzymes which degrade the organic substrate on which they are growing and yield smaller subunits. These in turn are absorbed into the body of the fungus whereby they are metabolized and the organism derives energy to carry on vital processes.
One such source of energy is raw, unseasoned wood produced from the activities of sawmills. The sawn logs represent a rich source of organic and inorganic compounds contained within a moist cellulosic matrix. Sawmills characteristically stack raw lumber outside in order to air dry (cure). During this relatively slow process of drying, the lumber is continuously being assaulted by fungal spores whose germination and growth on the wood surface may lead to significant economic loss to the sawmill as a result of surface disfigurement. In addition, other fungal species may reside on the wood which actually decay or diminish the structural integrity of the wood by enzymatically hydrolyzing the cellulose and/or lignin within the primary and secondary cell walls.
The lumber industry controls these fungal problems through the application of chemicals to the freshly sawn wood. Chemicals which have experienced widespread use in this industry, such as pentachlorophenol (PCP), 2-thiocyanomethylthiobenzothiazole (TCMTB), 3-iodo-propynylbutylcarbamate (IPBC), and disodium octaborate tetrahydrate (available commercially as Tim-Bor.RTM.), also exhibit disadvantages.
For instance, the organic antifungal agents PCP, TCMTB, and IPBC have been the objects of increasing environmental concern and legal restrictions of usage relative to their alleged contamination of the environment as well as complaints related to worker exposure. The borates also have a major disadvantage in that they will leach from treated wood when the wood is exposed to water. The net result of this is to reduce the effective concentration of borate in the wood and compromise its fungistatic activity.
The bactericidal and fungicidal activities of ionene polymers are known and have been described by Rembaum, A., "Biological Activity of Ionene Polymers," 22nd Applied Polymer Symposium, 299-317 (1973). The microbicidal property of ionenes have been disclosed in U.S. Pat. Nos. 4,018,592, 3,771,989, 4,054,542, 4,506,081, 4,111,679, 4,089,977, and 4,140,798. The biocidal activities of ionenes, however, are greatly reduced in systems possessing negatively charged fibers such as those represented by pulp slurries and wood. Moreover, the fungicidal activity of ionene is relatively poor compared with their algicidal and bactericidal activities.
Wood preservative compositions containing borates and alkyl-ammonium type compounds have also been disclosed in Japanese Patent No. 58/189-104.